Oligoacetic Acid Characterization by Isocratic and Linear Salt Gradient Anion-Exchange Chromatography

A reversed-phase high-performance liquid chromatographic procedure for the simultaneous determination of impurities associated with pseudoephedrine hydrochloride (PSEH) and naproxen sodium (NapNa) is developed and validated. The method is developed using a Waters Spherisorb cyano column (5 miue m, 250 x 4.6 mm). An isocratic elution in a water-acetonitrilemethanol-triethylamine mixture (850:73:75:5) is adjusted to a pH of 3.7 + 0.02 with formic acid as the mobile phase. The UV detection was set at 260 nm, and the wavelength was switched to 235 nm before the elution of the last component, 2-ethyl-6-methoxy-naphthalene (EMN). The method is shown to be linear at a concentration range of 0.24 to 1.92 miue g/mL for benzaldehyde, benzoic acid, and 2-(methylamino)-propiophenone hydrochloride, which are known impurities of PSEH. The NapNa impurities, 2-(6ʹ-hydroxy-2ʹ-naphthyl) propionic acid, 2-hydroxy6-methoxy-naphthalene, 1-(6ʹ-methoxy-2ʹ-naphthyl)ethanol, 2-acetyl-6-methoxy-naphthalene, and EMN are also demonstrated to be linear at a concentration range of 0.44 to 3.52 miue g/mL. Under the chromatographic conditions of the method, all impurities are resolved from the active components.